Gelatinous and soft-bodied zooplankton in the Northeast Pacific Ocean: Phosphorus content and potential resilience to phosphorus limitation

Marine ecosystems on continental shelves face multiple challenges due to anthropogenic disturbances, many of which can change the seawater stoichiometry (C:N:P) and consequently elemental ratios of phytoplankton. This change in food quality may not be tolerated by all grazers and predators. Gelatinous and soft-bodied zooplankton (GZ) might be more resilient to such changes. We sampled GZ species in neritic and oceanic waters of the Northeast Pacific off British Columbia, Canada, determined their phosphorus (P) content and elemental ratios (C/P, N/P), and analysed intraspecific variability associated with size and ontogeny. P content was measured for twelve GZ taxa. P % DW (dry weight) decreased with size for the hydrozoan Aequorea sp., scyphozoans Aurelia labiata, Cyanea capillata, and the thaliacean Salpa aspera, and differed significantly for two development stages of the salp S. aspera. While C/P and N/P were mostly size and stage independent, they were highly variable. C/P values of GZ were generally higher than values of crustacean zooplankton, indicating that GZ represent poor-quality prey for non-GZ predators, and that GZ may have a higher resilience towards P-limited (low quality) prey. Changing ocean conditions and nutrient stoichiometry of prey may favour GZ, although large variability in P dynamics among GZ taxa and uncertainty about future ocean stoichiometry changes make generalisations difficult.